The present invention relates to a new and improved method of, and apparatus for, determining the injection pressure during injection operations performed during construction work.
Generally speaking, the method and apparatus of the present invention rely upon measuring the pressure of the injection medium by means of a pressure measuring device.
In order to determine the injection pressure within boreholes it is already known in this technology to determine by computations the injection pressure. This is accomplished by taking into account the pressure generated by the injection pump and the characteristics of the inflow line leading to the boreholes and through which flows the injection medium. Since the magnitudes needed for such computations are not always sufficiently accurately known and, under circumstances, can fluctuate during the injection operation, it is not possible to determine in this fashion with sufficient accuracy the injection pressure.
Equally, it is known from Swiss Pat. No. 609,423 to arrange at the outlet of a distribution compartment or chamber, coupled with a pump device, within each outbound line a throughflow regulation valve and a measuring device for measuring the pressure prevailing downstream of such regulation valve. However, the measuring devices are located at an appreciable distance from the injection site or location, so that the pressure measured by such measuring devices only approximately corresponds to the injection pressure prevailing in the boreholes.
In order to be able to detect the actual pressure prevailing at the injection site it has already been proposed to arrange a pressure measuring device forwardly of the outlet opening of the infeed line arrangement. This pressure measuring device is impinged or has flowing therearound the injection medium effluxing from the infeed line arrangement or infeed line. Since the pressure measuring device is located completely within the flow of the injection material the danger exists that material will deposit at dead spaces and at the supports or holders by means of which the pressure measuring device is connected with the infeed line arrangement. Additionally, the flow of the injection medium is disturbed by the pressure measuring device. It is for these reasons that the obtained measurement results are falsified and, thus, do not portray the desired accurate picture of the injection pressure. Furthermore, there is also present the danger that the pressure measuring device will remain anchored in the borehole due to solidification of the injection material and no longer can be removed from such borehole in conjunction with the infeed line arrangement.